/* istanbul ignore next */

// import Vue from 'vue'

const isServer = false
const SPECIAL_CHARS_REGEXP = /([:\-_]+(.))/g
const MOZ_HACK_REGEXP = /^moz([A-Z])/
const ieVersion = isServer ? 0 : Number(document.documentMode)

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const trim = function (string) {
    return (string || '').replace(/^[\s\uFEFF]+|[\s\uFEFF]+$/g, '')
}
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const camelCase = function (name) {
    return name.replace(SPECIAL_CHARS_REGEXP, function (_, separator, letter, offset) {
        return offset ? letter.toUpperCase() : letter
    }).replace(MOZ_HACK_REGEXP, 'Moz$1')
}

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export const on = (function () {
    if (!isServer && document.addEventListener) {
        return function (element, event, handler) {
            if (element && event && handler) {
                element.addEventListener(event, handler, false)
            }
        }
    } else {
        return function (element, event, handler) {
            if (element && event && handler) {
                element.attachEvent('on' + event, handler)
            }
        }
    }
})()

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export const off = (function () {
    if (!isServer && document.removeEventListener) {
        return function (element, event, handler) {
            if (element && event) {
                element.removeEventListener(event, handler, false)
            }
        }
    } else {
        return function (element, event, handler) {
            if (element && event) {
                element.detachEvent('on' + event, handler)
            }
        }
    }
})()

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export const once = function (el, event, fn) {
    var listener = function () {
        if (fn) {
            fn.apply(this, arguments)
        }
        off(el, event, listener)
    }
    on(el, event, listener)
}

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export function hasClass (el, cls) {
    if (!el || !cls) return false
    if (cls.indexOf(' ') !== -1) throw new Error('className should not contain space.')
    if (el.classList) {
        return el.classList.contains(cls)
    } else {
        return (' ' + el.className + ' ').indexOf(' ' + cls + ' ') > -1
    }
}

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export function addClass (el, cls) {
    if (!el) return
    var curClass = el.className
    var classes = (cls || '').split(' ')

    for (var i = 0, j = classes.length; i < j; i++) {
        var clsName = classes[i]
        if (!clsName) continue

        if (el.classList) {
            el.classList.add(clsName)
        } else if (hasClass(el, clsName)) {
            curClass += ' ' + clsName
        }
    }
    if (!el.classList) {
        el.className = curClass
    }
}

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export function removeClass (el, cls) {
    if (!el || !cls) return
    var classes = cls.split(' ')
    var curClass = ' ' + el.className + ' '

    for (var i = 0, j = classes.length; i < j; i++) {
        var clsName = classes[i]
        if (!clsName) continue

        if (el.classList) {
            el.classList.remove(clsName)
        } else if (hasClass(el, clsName)) {
            curClass = curClass.replace(' ' + clsName + ' ', ' ')
        }
    }
    if (!el.classList) {
        el.className = trim(curClass)
    }
}

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export const getStyle = ieVersion < 9 ? function (element, styleName) {
    if (isServer) return
    if (!element || !styleName) return null
    styleName = camelCase(styleName)
    if (styleName === 'float') {
        styleName = 'styleFloat'
    }
    try {
        switch (styleName) {
        case 'opacity':
            try {
                return element.filters.item('alpha').opacity / 100
            } catch (e) {
                return 1.0
            }
        default:
            return (element.style[styleName] || element.currentStyle ? element.currentStyle[styleName] : null)
        }
    } catch (e) {
        return element.style[styleName]
    }
} : function (element, styleName) {
    if (isServer) return
    if (!element || !styleName) return null
    styleName = camelCase(styleName)
    if (styleName === 'float') {
        styleName = 'cssFloat'
    }
    try {
        var computed = document.defaultView.getComputedStyle(element, '')
        return element.style[styleName] || computed ? computed[styleName] : null
    } catch (e) {
        return element.style[styleName]
    }
}

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export function setStyle (element, styleName, value) {
    if (!element || !styleName) return

    if (typeof styleName === 'object') {
        for (var prop in styleName) {
            if (styleName.hasOwnProperty(prop)) {
                setStyle(element, prop, styleName[prop])
            }
        }
    } else {
        styleName = camelCase(styleName)
        if (styleName === 'opacity' && ieVersion < 9) {
            element.style.filter = isNaN(value) ? '' : 'alpha(opacity=' + value * 100 + ')'
        } else {
            element.style[styleName] = value
        }
    }
}

export function isVNode (node) {
    return typeof node === 'object' && node.hasOwnProperty('componentOptions')
}
